C++ Manipulators

1. std::setw(int width)

The setw manipulator sets the field width for the next input or output operation. It is particularly useful for formatting output columns.

#include <iostream>
#include <iomanip>

int main() {
    std::cout << std::setw(10) << "Name" << std::setw(10) << "Age" << std::endl;
    std::cout << std::setw(10) << "John" << std::setw(10) << 25 << std::endl;
    std::cout << std::setw(10) << "Alice" << std::setw(10) << 30 << std::endl;

    return 0;
}

2. std::setprecision(int n)

The setprecision manipulator sets the precision (number of decimal places) for floating-point numbers.

#include <iostream>
#include <iomanip>

int main() {
    double pi = 3.1415926535;

    std::cout << std::setprecision(4) << pi << std::endl;  // 3.142
    std::cout << std::setprecision(2) << pi << std::endl;  // 3.1

    return 0;
}

3. std::fixed and std::scientific

These manipulators control the format of floating-point numbers. std::fixed forces fixed-point notation, while std::scientific forces scientific notation.

#include <iostream>
#include <iomanip>

int main() {
    double number = 12345.6789;

    std::cout << std::fixed << number << std::endl;      // 12345.678900
    std::cout << std::scientific << number << std::endl;  // 1.234568e+04

    return 0;
}

4. std::setfill(char c)

The setfill manipulator sets the fill character used in field width.

#include <iostream>
#include <iomanip>

int main() {
    std::cout << std::setfill('*') << std::setw(10) << "Hello" << std::endl;  // *****Hello

    return 0;
}

5. std::left, std::right, and std::internal

These manipulators control the alignment of output within a field. std::left (default) left-aligns the output, std::right right-aligns it, and std::internal aligns the sign of the value to the left and the digits to the right.

#include <iostream>
#include <iomanip>

int main() {
    int number = -42;

    std::cout << std::setw(5) << std::left << number << std::endl;    // -42
    std::cout << std::setw(5) << std::right << number << std::endl;   //   -42
    std::cout << std::setw(5) << std::internal << number << std::endl;  // -  42

    return 0;
}

6. std::boolalpha and std::noboolalpha

These manipulators control the output of boolean values. std::boolalpha sets the output to display true or false, while std::noboolalpha uses the numeric representation.

#include <iostream>
#include <iomanip>

int main() {
    bool flag = true;

    std::cout << std::boolalpha << flag << std::endl;      // true
    std::cout << std::noboolalpha << flag << std::endl;     // 1

    return 0;
}

These manipulators can be used individually or combined to control the formatting of output in a variety of ways. They are often used with the insertion (<<) and extraction (>>) operators to customize the appearance of data in the console or other streams.